As advanced features such as artificial intelligence (AI) and complex human-machine interfaces (HMI) with rich graphics become increasingly common in applications, product designers are beginning to search for more powerful microcontroller units (MCUs). But at the same time, designers are also required to develop the most cost-effective products and abandon these flashy features. Under these conflicting pressures, it is imperative to choose an MCU that can be easily expanded to meet different market demands.

The accelerating pace of innovation has also intensified this pressure. The application requirements may undergo unexpected changes, so it is crucial to easily obtain alternative MCUs. In addition, future applicability and reuse issues must also be considered. If design elements can be reused in other projects, it can significantly save time and costs.

One way to address these challenges is to choose MCU series with a wide range of options. STMicroelectronics' STM32H7 is a good example. This series offers both cost-effective entry-level 32-bit MCUs and feature rich dual core MCUs.

This article takes the functions of STM32H7 series as an example and focuses on the standards that should be considered when choosing MCU series. In addition, development boards and tools suitable for STM32H7 MCU were introduced, and how to use these infrastructures to initiate projects was explained.

Factors for achieving flexibility and scalability of MCU series
When searching for a flexible MCU series, numerous factors must be considered. Providing a wide range of performance and power level options is particularly important. The preferred MCU series should include various clock speed and core options optimized for different objectives. For example, low-power Arm ® Cortex ®- M4 and high-performance Arm Cortex-M7.

This series should include MCUs with basic processing capabilities and options with expansion capabilities. Many applications require data protection and secure communication. Hardware based encryption, secure boot, and encryption accelerators are crucial for these use cases. Similarly, digital signal processors (DSPs) and floating-point instructions are also crucial for data intensive applications.

The MCU series should also provide various sizes of RAM and flash memory to accommodate applications ranging from simple ones to those that require a large amount of software frameworks or data storage space. These MCUs should provide external memory interfaces for applications that exceed their internal memory capacity to provide necessary scalability.

Finally, MCU series with more peripheral options can also cope with a wider range of applications. It is crucial to ensure that the MCU series includes advanced I/O options such as USB, Ethernet, Bluetooth, and Wi Fi, as it may be difficult to add these interfaces as upgrades in subsequent designs. Ideally, the selected MCU series should provide pin compatibility within its product range, so that hardware upgrades or downgrades can be achieved without making significant design changes to the printed circuit board (PC board).

Development tools should support the entire MCU series from a software perspective. In order to accelerate development speed, there should also be a unified software application programming interface (API) and a powerful set of libraries, middleware, and real-time operating system (RTOS).

STM32H7: Multi functional Case Study
The STM32H7 series from STMicroelectronics is a model MCU series that meets these standards. As shown in Table 1, this series has high scalability and is built around the Arm Cortex-M7, covering both basic and advanced MCUs. This series is divided into four sub series, each optimized for different applications.

Main features of MCU core and clock maximum flash/RAM
Value Series 280 MHz to 550 MHz
Arm Cortex-M7 128 KB Flash Memory
1 MB RAM Low cost, Ethernet QSPI、TFT
Single core series from 280 MHz to 550 MHz
Arm Cortex-M7 2 MB Flash Memory
1.4 MB RAM TFT、 Ethernet Q-SPI、 low power consumption
Dual core series 480 MHz
Arm Cortex-M7 +
240 MHz
Arm Cortex-M4 2 MB flash memory
1 MB RAM switch mode power supply (SMPS), TFT-LCD, MIPI-DSI, JPEG
BootFlash series 600 MHz
Arm Cortex-M7 external flash memory, 620 KB RAM NeoChromium GPU, I3C, XiP, USB PHY
Table 1: Main highlights of the four sub series of STM32H7 series. (Table source: Author, using raw materials provided by STMicroelectronics)

The speed range of the Value Series is from 280 MHz to 550 MHz, using 128 KB embedded flash memory and 1 MB RAM. This series supports various communication interfaces and external memory expansion, providing a cost-effective solution for performance oriented systems. STM32H750VBT6 is such an MCU, which adopts a 14 x 14 mm 100-LQFP package.

The operating speed range of the single core series is also from 280 MHz to 550 MHz. This series offers up to 2 MB of flash memory and 1.4 MB of RAM, making it perfect for applications that require rich user interfaces and real-time control. One example is STM32H743IIK6, which uses a 10 x 10 mm 201-UFBGA package.

The dual core series adopts an auxiliary Arm Cortex-M4 core optimized for efficiency. Embedded switch mode power supply (SMPS) can improve power efficiency. Other advanced peripherals include TFT-LCD, MIPI-DSI, and hardware JPEG codec. A typical example is STM32H747AII6, which uses a 7 x 7 mm 169-UFBGA package.

The BootFlash series is known for its high performance, with speeds up to 600 MHz. This series is designed to support real-time in place execution (XiP) applications and is equipped with 64 KB boot flash and 620 KB RAM. In addition, some models in the series can also be equipped with NeoChrom GPU to enhance graphics acceleration capabilities. A typical representative of this series is STM32H7R3Z8J6, which adopts a 10 x 10 mm 144-UFBGA package.

Benefits of compatibility with STM32F4 and STM32F7 series
STM32H7 is one of the many product lines of STMicroelectronics MCU, and its pin layout is compatible with similar STM32F4 and STM32F7 series, and can adapt to the most common packaging forms. These MCUs are all based on the Arm Cortex-M core and have similar peripheral and GPIO pin layouts. These commonalities enable designers to easily migrate between MCUs without making significant hardware changes. When upgrading products or designing new products based on different features of each series, this compatibility can shorten development time and reduce costs.

In addition, all MCUs are supported by the same software development ecosystem, including STM32CubeMX for configuring and initializing code generation, and STM32CubeIDE for development and debugging. This compatibility ensures that software components, middleware, and application code can be reused in any series of projects, further accelerating the development cycle.

Start using STM32H7 series MCU
Starting to use STM32H7 MCU involves several key steps as well as efficient use of development boards and tools. The following step-by-step guide will introduce how to start developing using these powerful microcontrollers.